Microfluidics deals with the behavior, precise control, and manipulation of fluids that are geometrically constrained to a small, typically sub-millimeter, scale. It is a multidisciplinary field at the intersection of engineering, physics, chemistry, nanotechnology, and biotechnology. A microfluidic chip refers to a system or device having micro-channels or micro-chambers that are generally fabricated on a substrate. The length scale of the micro-channels and micro-chambers is typically on the micron or submicron scale. For example, the micro-channels and the micro-chambers typically have at least one cross-sectional dimension in the range of approximately 0.1 micron to approximately 1000 microns, e.g., approximately 0.1 micron to approximately 500 microns.